<template>
	<ul class="list">
		<li class="item"
		v-for="item of letters"
		:key="item"
    :ref="item"
    @touchstart.prevent="handleTouchStart"
    @touchmove="handleTouchMove"
    @touchend="handleTouchEnd"
		@click="handleLetterClick">
		{{item}}
		</li>
    </ul>
</template>
<script>
export default {
  name: 'CityAlphabet',
  props: {cities: Object},
  data () {
    return {
      touchStatus: false,
      startY: 0,
      timer: null
    }
  },
  computed: {
    letters () {
      const letters = []
      for (let i in this.cities) {
        letters.push(i)
      }
      return letters
    }
  },
  updated () {
    this.startY = this.$refs['A'][0].offsetTop
  },
  methods: {
    getinHome () {
      this.$router.push({
        path: '/'
      })
    },
    handleLetterClick (e) {
      this.$emit('change', e.target.innerText)
    },
    handleTouchStart () {
      this.touchStatus = true
    },
    handleTouchMove (e) {
      if (this.touchStatus) {
        if (this.timer) {
          clearTimeout(this.timer)
        }
        this.timer = setTimeout(() => {
          const touchY = e.touches[0].clientY - 86
          const index = Math.floor((touchY - this.startY) / 20)
          if (index >= 0 && index < this.letters.length) {
            this.$emit('change', this.letters[index])
          }
        }, 8)
      }
    },
    handleTouchEnd () {
      this.touchStatus = false
    }
  }
}
</script>
<style lang="stylus" scoped>
@import '~assets/variles.styl'
.list
	position absolute
	display: flex
	flex-direction: column
	justify-content: center
	right: 0
	top: 1.72rem
	bottom: 0
	width: .4rem
	.item
		text-align: center
		line-height: .4rem
		color: $bgColor
</style>
